The Winter Activity and Movements,
Winter diet, and Breeding Biology
of the Fisher (Martes pennanti)
in Southeastern Manitoba

Richard D. Leonard

Department of Zoology, University of Manitoba, Winnipeg, Manitoba R3T 2N2

Present address: Parks Canada, Prairie Region, Confederation Building, 4th Floor, 457 Main Street, Winnipeg, Manitoba R3B 3E8




Leonard, R.D. 1980. The Winter Activity and Movements, Winter diet, and Breeding Biology of the Fisher (Martes pennanti) in Southeastern Manitoba. M.Sc. Thesis, University of Manitoba. 181 pp.



From May 1975 to June 1977 aspects of the ecology of the fisher were studied in the field by use of radio-telemetry, tracking and track observations. Information on reproduction, food habits, age and sex distributions, and physical condition was gathered from analysis of 195 trapper-caught fisher carcasses collected from four areas during the winters of 1972-73 to 1977-78.

During the winters of 1975-76 and 1976-77 the upper levels of the snow cover affected fisher locomotion and extensiveness of activity. Changes in the use of gaits and cover types were qualitatively correlated with physical variations in the snow cover. An almost complete depression of fisher activity occurred in the intensive tracking unit during periods in January and February 1975-76 and January 1976-77 when the area was covered by extremely soft snow. Effects of temperature, prey availability and social behaviour could not be separated absolutely from the effects of snow cover, but application of snow factors into an established ecological energetics model developed to estimate energy requirements of free-ranging fishers indicated that soft snow could greatly increase energy expenditures of active fishers. The response of fishers to snow cover was believed to be unique for boreal Martes. Information from age class structure and radio-telemetry indicated that juveniles moved more extensively than adults during winter.

Twenty-two genera and 20 species of prey and carrion were identified from alimentary tracts of 120 fishers that contained food items. Mammals, particularly snowshoe hares (Lepus americanus) and birds were the dominant food sources. Proportions of foods from scats collected in the intensive study area did not differ appreciably from proportions of food in alimentary tracts. Porcupine was the only food that showed significant geographic and sex differences in the diet. Fishers responded functionally to increasing numbers of snowshoe hares. Use of other types of food and the number of different foods declined as the proportion of snowshoe hares in alimentary tracts increased. Estimates of daily consumption rate of fishers also supported occurrence of a functional response and substantiated the importance of snowshoe hares in the winter diet. Use of small mammals, frequency of empty alimentary tracts, and standard deviations of condition indices were related to the proportion of hares in alimentary tracts.

Presence of pregnant females in the yearling age class, increased tract volume and follicular development of late-winter juveniles and observations of a tract of a recently-bred juvenile indicated that first reproduction of females occurred at the end of the first year of the juvenile age class. Winter maturation of testes followed a similar pattern for juveniles and adults. All males tested in March were spermatic, but none were spermatic earlier in the winter. By March, bacula from juveniles approached the weight of bacula from adults. Estrus and parturition occurred in late March and April. Uniform development of early-winter juveniles suggested a restricted whelping period and possibly a restricted mating period occurred for all ages of reproducing females. The mean (3.5) and mode (3) corpora lutea counts for fertile females differed little from reports from other regions of the fisher's range. Age-related fertility rates appeared to exist, but indices of fertility and productivity remained relatively constant from 1972 to 1978, suggesting no time-specific changes in reproduction. Movements of a radio-collared adult female during active pregnancy were not extensive. It was believed that the reduction in activity was a strategy to conserve energy for growth of foetuses. The movements of this radio-collared adult female were monitored after she whelped kits in a tree den. She spent more time away from her kits as time in the denning period progressed, but she did not travel progressively farther each day. Movements of the female were extensive and covered most of her formerly-established home range. This behaviour was attributed to the necessity of using a well-known home range for more successful foraging, maintaining non-breeding period patterns of social organization and diverting male courtship activities from the den area. The diet of the female early in the denning period, as determined from analysis of scats, differed little from the winter diet. Radio-telemetry and tracking evidence during the breeding period suggested that adult females in estrus remained relatively sedentary, but males appeared to abandon non-breeding period territoriality to seek out females in estrus. No male-male physical interactions were observed in the field, but the presence of minor skull injuries in breeding-age males implied that some form of interaction could occur.

Key Words: Fisher, Martes pennanti, reproduction, breeding systems, Manitoba.



This page created March 13, 1999.




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